1. Field of the Invention
This invention relates to a process for producing an endless belt, and more particularly, to a process for producing an endless belt used in, e.g., intermediate transfer members and transfer material carrying members for electrophotography. This invention also relates to an image forming apparatus having an endless belt formed by such production process.
2. Related Background Art
Compared with image forming apparatus in which images are transferred from a first image bearing member to a second image bearing member (transfer material) fastened or attracted onto a transfer drum (Japanese Patent Application Laid-open No. 63-301960), image forming apparatus making use of intermediate transfer belts have an advantage that a variety of second image bearing members can be selected without regard to their width and length, including thin paper (40 g/m.sup.2 paper) and up to thick paper (200 g/m.sup.2 paper) such as envelopes, post cards and labels. This is because any processing or control (e.g., the transfer material is held with a gripper, attracted, and made to have a curvature) is not required for the second image bearing member transfer material.
Because of such an advantage, color copying machines and color printers making use of intermediate transfer belts have already begun to be available in the market.
Color image forming apparatus are also proposed which have a plurality of recording assemblies in which electrostatic latent images are formed on photosensitive members, the electrostatic latent images formed are developed and the developed images are transferred to a transfer material, where a color image is formed by transferring individual color images superimposingly to the transfer material while transporting it successively to the respective recording assemblies by means of a transfer material carrying member (transfer belt). Such image forming apparatus have an advantage that images can be reproduced in a short time because the color image is formed through one step.
Because of such an advantage, color copying machines and color printers making use of transfer belts have already begun to be available in the market.
Various processes for producing such intermediate transfer belts and transfer belts are already known in the art. For example, Japanese Patent Application Laid-open No. 3-89357 and No. 5-345368 disclose a process for producing a semiconducting belt by extrusion.
Japanese Patent Application Laid-open No. 5-269849 also discloses a process in which a belt is obtained by joining both ends of a sheet to bring it into a cylindrical form. Japanese Patent Application Laid-open No. 9-269674 discloses a process in which a belt is obtained by forming a multi-layer coating film on a cylindrical substrate and finally removing the substrate. Meanwhile, Japanese Patent Application Laid-open No. 5-77252 discloses a seamless belt obtained by centrifugal molding.
For example, in the extrusion, the production of an endless belt having a thickness of 100 .mu.m or smaller involves considerable difficulties, tending to cause uneven wall thickness and uneven electrical resistance. Also, in the case when both ends of a sheet are joined, the difference in height and decrease in tensile strength at the joint come into question. Still also, processes making use of solvents as in cast molding, coating and centrifugal molding require many steps of preparing a coating solution, coating it and removing the solvent, resulting in a high cost.